. >> reporter: mandela, as an ex-president, met with george w. bush in 2005. but there was no love lost there. mandela was one of bush's harshest critics when it came to iraq. when we talked to bush about the ailing mandela earlier this year, there were no hard feelings. >> he promoted freedom. he was a really great leader. he was smart and capable. and made his mark. >> reporter: obama only met mandela once. ever so briefly as a junior senator. but his connection may be the most profound. it was mandela, he says, who awakened him to the wider world. inspiring him to political activism. >> he gave me a sense of what human beings can do when guided by their hopes, not by their fears. >> reporter: in other words, there night not be a president obama if not for nelson mandela. for "this week." jonathan karl, abc news, washington. >>> and we're lucky now to be joined by four individuals who had unique working relationships with nelson mandela. bill keller. dr. gay mcdougall, who campaigned for his release from prison. stan greenberg, his pollster and strategist. a